A security guard working in Oscar Pistorius' gated community says the athlete told him everything was "fine" when he called to investigate neighbours' reports of gunshots on the night Reeva Steenkamp was killed.

Pieter Baba, who drove with another guard and made a phone call to Pistorius from outside the Olympian's villa in the pre-dawn hours of Feb. 14 last year, testified Friday: "that's when Mr. Pistorius said to me everything is fine."

Baba said Pistorius called him back but was crying, didn't say anything and the line "went off."

Baba said he told a fellow security guard: "not everything was in order as Mr. Pistorius was telling me."

Pistorius is charged with murder. He says he shot Steenkamp by mistake, thinking she was an intruder.

Earlier on Friday, a former girlfriend of Oscar Pistorius testified that Pistorius carried a gun with him "all the time" when they were dating, and on one occasion he fired it out of a car's sunroof soon after a policeman stopped the car they were in for speeding.

Samantha Taylor said her relationship with Pistorius ended when he cheated on her with Steenkamp. The court adjourned briefly after Taylor broke down in tears.

Defence lawyer Barry Roux said he would produce emails between Taylor and Pistorius to show the cheating allegation was untrue.

First responder continues testimony

A neighbour of Pistorius testified earlier Friday that the bangs he heard after a woman's screams on the night of Steenkamp's shooting were likely too quick to be the sounds of a cricket bat on a door, as the star athlete's defence team claims.

Johan Stipp, a radiologist and one of the first responders to the incident, testified that he earlier heard a woman's screams and a man's shouts before a second grouping of sounds that he said were gunshots on the night Pistorius killed girlfriend Steenkamp.

Prosecutor Gerrie Nel asked him if bangs he heard after the woman's screams could have been Pistorius swinging a bat at the toilet cubicle door to get to a mortally wounded Steenkamp, but Stipp said the noises came in too quick of a succession to be bat swings.

The argument over the sequence of events in the early hours of Valentine's Day last year is a critical part of the case against Pistorius, a double-amputee runner who competed at the Olympics in 2012 and became a globally recognized figure.

He is charged with premeditated murder in Steenkamp's shooting death.

Pistorius says he screamed before he shot Steenkamp, thinking he was telling a dangerous intruder in his home to get out. He also says he screamed for help after, but Steenkamp was silent throughout.

Stipp, who lived in a house behind and across the road from Pistorius's villa, also repeatedly used the word "intermingled" to describe the sounds of a man shouting and a woman screaming, saying he believed two people were yelling at the time.

That's also a central part of the prosecution's case, insisting the couple had an argument before Pistorius intentionally shot Steenkamp through a locked toilet door in his home.

Stipp also said he saw a bathroom light on in Pistorius's house before the sound of the woman's screams. The defence says it will show that only Pistorius screamed during the shooting and his voice may have been mistaken for Steenkamp because they say it is high-pitched when he is anxious.

Continuing his cross-examination of Stipp, Roux said audio tests conducted after the shooting would show that Stipp couldn't have heard a woman screaming from the toilet cubicle as Pistorius shot through the door.

Roux also asked Stipp if he heard the emotion in the woman's screams that night, the "blood-curdling" yells that other witnesses who lived further away from the athlete's villa have testified to.

"Not at that moment. No, I didn't," Stipp said.

Stipp described in his testimony Thursday how he was one of the first to the scene of the shooting and found Pistorius knelt next to a fatally injured Steenkamp. Stipp said Pistorius then told him that he had shot Steenkamp thinking she was a burglar.

Roux said Friday: "I've asked him (Pistorius) about that. He's told me he has no memory of that. He's not saying it was not so. He has no memory."